The objective of this research is to identify the functions of the early gene products of the oncogenic virus polyoma, their role in viral DNA replication during lytic infection and the mechanism by which they alter the control of DNA synthesis in cells transformed by the virus. An in vitro system for viral DNA replication will be used to develop an in vitro complementation assay for temperature sensitive early mutant functions required during replication. Replicative complexes from infected cells will be analyzed for their cellular and viral components. Cell lines transformed by temperature sensitive mutants of polyoma will be established to study changes in their DNA replication patterns after shift from nonpermissive to permissive temperature and vice versa.